# The registry module can be extended into a class to enable
# by name and by id registry storage and lookup
module Registry


  # Sets up the registry
  def prepare_registry
    @registry_by_id              ||= {}
    @registry_by_name            ||= {}
  end

  def registry_by_name
    prepare_registry
    return @registry_by_name 
  end

  # Gets the id and name for the object for use with the registry
  def get_registry_id_and_name(obj, id = nil, name = nil)
    id      = obj.id          if obj.respond_to? :id
    name    = obj.name        if obj.respond_to? :name
    name    = (name ? name.to_s.to_sym : id.to_s.to_sym)
    
    return id, name
  end
  
  # Registers the object with the given numeric ID and name
  # The obj should respond to :name and :id
  def register(obj, id = nil, name = nil)
    prepare_registry
    id, name                       = get_registry_id_and_name(obj, id, name)
    @registry_by_id[id]            = obj
    @registry_by_name[name.to_sym] = obj
  end


  # Unregisters the object
  def unregister(obj, id = nil, name = nil)
    prepare_registry
    id, name                        = get_registry_id_and_name(obj, id, name)
    @registry_by_id[id]             = nil
    @registry_by_name[name.to_sym]  = nil
  end

  # Looks up an item in the registry by name or by id.
  # If thing responds to :to_sym it's looked up as a name,
  # otherwise it's looked up by numerical
  def [](name_or_id)
    prepare_registry
    if name_or_id.respond_to? :to_sym
      return @registry_by_name[name_or_id.to_sym]
    else
      return @registry_by_id[name_or_id]
    end
  end
  
  # Other way to say self[]
  def lookup(name_or_id)
    return self[name_or_id]
  end
  
  # Calls a callback for each registry item with name, item
  def registry_each_name
    @registry_by_name.each do | n, e |
      yield n, e
    end
  end
  
    # Calls a callback for each registry item with id, item
  def registry_each_id
    @registry_by_id.each do | id, e |
      yield id, e
    end
  end


end